Do you do much cold weather driving? It's not just snow that summer performance tires are bad in, it's cold weather. Anything below maybe 45 degrees F and they turn hard and lose a lot of grip.

Wear differs between various models and brands, but generally speaking, summer performance will wear quicker than all seasons, but offer more grip, it's a trade-off. So your switch to the Contis should gain you performance (a fair amount) but will wear quicker.

Also, if you're just getting new fronts, I wouldn't recomend mis-matching with the rears. The different grip offered by a different kind of tire could cause unwanted handling changes and even make the car unstable during handling (depending on if it indroduces over or understeer). If you're only replacing 2, you should match to what you have. Or get 4 new tires. That would be the rational advice anyway, you are free to do whatever you want smile